When building coreMQTT in Ubuntu 23.10 I get this error: raphy@raohy:~/libpeer/dependencies/coreMQTT$ gcc -I source/include/ -DMQTT_DO_NOT_USE_CUSTOM_CONFIG -I source/interface/ source/core_mqtt.c source/core_mqtt_state.c source/core_mqtt_serializer.c -o coreMQTT /usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/13/../../../x86_64-linux-gnu/Scrt1.o: in function `_start': (.text+0x1b): undefined reference to `main' collect2: error: ld returned 1 exit status What am I doing wrong? How make it work?